The present invention relates to an inspection apparatus that inspects a magnetic field generated from a magnetic device.
Means for inspecting write heads used for magnetic recording devices such as hard disks include: appearance inspection using a scanning electron microscope (SEM), an atomic force microscope (AFM), and optical means; electric inspection such as resistance measurement; and magnetic field measurement using a magnetic force microscope (MFM).
The appearance inspection using SEM is just applicable to a very small number of products as samples because an electron beam damages elements or a time loss results from vacuuming. The inspection using AFM or MFM consumes time in units of minutes when the measurement requires a resolution on the order of nanometers. The inspection is also just applicable to a very small part of products as samples.
The appearance inspection using optical means is capable of fast inspecting a shape failure in micrometers or the presence or absence of foreign particles. However, restrictions on a horizontal spatial resolution make it impossible to inspect the detailed shape of a write head or measure a magnetic field generated from the write head. The electric measurement using a head tester is widely used because the measurement can concurrently inspect many products at a time and inspect all products. The measurement has been expected to be used for a higher level of inspection because the measurement is suited for high value-added products.
Scanning probe microscopes (SPM) such as AFM and MFM two-dimensionally scan a probe along a surface under observation, making it difficult to shorten the measurement time. Various approaches have been attempted to speed up the measurement. For example, Japanese Published Unexamined Patent Application No. 2007-85764 discloses a step-in technology. Instead of two-dimensionally scanning a probe, the step-in technology discretely repeats contact with a sample and observes it only at contact points. The technology decreases observation points and aims at speeding up the observation.
As one feature, the step-in technology allows a probe to approach the sample surface approximately perpendicularly thereto, making it possible to more accurately measure steep shapes. As another feature, the step-in technology uses fewer measurement points than continuous scanning methods, making it possible to fast scan a large area.
On the other hand, the step-in technology performs discrete measurement and degrades the horizontal in-plane resolution when a large area is measured. Improving the recording density requires narrowing the write width for magnetic recording apparatuses such as hard disks, for example. Therefore, it is also necessary to narrow a writing magnetic field generated from a write head. In order to inspect and evaluate the writing magnetic field, the magnetic field detection method and the apparatus need to provide the spatial resolution of approximately one to ten nanometers precise enough to be capable of analyzing the writing magnetic field and need to be capable of measuring the magnetic field at a speed capable of inspecting all products.